CN104112811A - LED (light emitting diode) packaging method - Google Patents

Abstract

The invention discloses an LED packaging method, which belongs to the technical field of semiconductor packaging. In the present invention, the iron foil (8) is used as the conductive layer to carry out high-precision electroplating process many times, and combined with the photolithography process to realize the rewiring metal layer and metal block, and then encapsulating the rewiring metal layer and metal block with encapsulating resin to form a metal The lead frame body (1), and then the LED chip (2) is mounted and fixed on the metal lead frame body (1), and then the entire packaging structure is completed. The invention adopts a high-precision electroplating process to realize the metal lead frame body, overcomes the warping defect of the frame existing in the wet corrosion process, effectively solves the coordination problem of the chip mounting and wire bonding process, and improves the yield rate and consistency.

Description

A kind of packaging method of LED

technical field

The invention relates to an LED packaging method, which belongs to the technical field of semiconductor packaging.

Background technique

Under the background of energy saving and environmental protection, my country's LED industry is developing rapidly, and the development prospects of the LED industry are very promising. EMC (epoxy encapsulation material) packaging is one of the current high-end development directions of the LED industry. In the EMC packaging method, the lead frame is formed by a wet etching process, that is, the so-called half-etching process. The warpage of the lead frame itself formed by this process is relatively large, which makes it difficult to adjust the chip mounting and wiring process. , the loss of yield is large; at the same time, the etching precision of the lead frame formed by this process is low, and the consistency of the product is not good.

Contents of the invention

The purpose of the present invention is to overcome the disadvantages of the traditional lead frame packaged LED and provide an LED package method that improves the yield and consistency of products.

The purpose of the present invention is achieved like this :

A kind of packaging method of LED of the present invention, its technical process is as follows:

Take a carrier board and iron foil, and fix the iron foil on the carrier board;

Paste the photoresist film I on the iron foil, and form the opening pattern of the photoresist film I by setting the pattern, exposing and developing in sequence;

Electroplate metal in the opening pattern of the photoresist film I to form a rewiring metal layer, and electroless nickel/gold plating on the surface of the rewiring metal layer, and remove the remaining photoresist film through a deglue process;

Paste the photoresist film II on the iron foil that has completed the rewiring metal layer, and sequentially set the pattern, expose, and develop to form the opening pattern of the photoresist film II to expose the rewiring metal layer;

Metal block is formed by electroplating in the opening pattern of photoresist film II, and the remaining photoresist film is removed by deglue process, and then the wiring metal layer is connected to the metal block one-to-one to form metal block I, metal block II, and metal group respectively. Block III;

Encapsulating the top of the iron foil forming the metal block I, the metal block II, and the metal block III to form an encapsulation layer;

The encapsulation layer on the top of the iron foil is thinned by grinding and polishing, exposing one end surface of metal block I, metal block II, and metal block III, and the metal block I, metal block II, and metal block Electroless nickel/gold plating on the end face of Ⅲ;

Flip the above-mentioned packaged structure up and down 180°, take out the download board, and corrode the iron foil to expose the other end faces of metal block I, metal block II, and metal block III. Ⅱ. Electroless nickel/gold plating layer on the end face of metal block Ⅲ;

Put adhesive I on the surface of metal block III with nickel/gold layer, and attach the back of the LED chip to the area of metal block III through adhesive I;

Wire bonding, connect the electrodes of the LED chip to the rewiring metal layers of the metal block I and the metal block II through the lead wires;

A dot package, which wraps the LED chip and its leads;

The above packaged LED package structure is cut into individual packages.

The boundary of the rewiring metal layer of the metal block III in the present invention is not smaller than the boundary of the LED chip.

The opening size of the opening pattern of the photoresist film I described in the present invention is not smaller than the opening size of the corresponding opening pattern of the photoresist film II.

The metal block I, the metal block II and the metal block III in the present invention are all T-shaped.

The heights of metal block I, metal block II and metal block III in the present invention are equal.

The metal block of the present invention has a height of 100 microns to 200 microns.

The material of the metal block in the present invention is metal copper.

The redistribution metal layer of the present invention is made of metal copper.

The present invention further includes a step after wiring: spotting adhesive II on the joints of the leads and the metal block I and the metal block II.

The present invention also includes a process step before the dot encapsulation: spraying fluorescent substances on the light-emitting surface of the LED chip.

The invention adopts a photolithography process combined with an electroplating process to realize the rewiring metal layer and the metal block of the metal lead frame body, thereby improving the processing accuracy of the metal lead frame.

The beneficial effects of the present invention are:

The metal lead frame of the present invention is realized by a high-precision electroplating process, which overcomes the warping defect of the frame existing in the wet etching process, effectively solves the problem of coordination between chip mounting and wire bonding processes, and improves the yield rate and consistency.

Description of drawings

Fig. 1 is the schematic flow sheet of a kind of packaging method of LED of the present invention;

2 is a schematic cross-sectional view of an embodiment of a packaging structure of a LED packaging method according to the present invention;

Fig. 3 is a schematic top view of the positional relationship of the components in Fig. 2;

4 to 17 are schematic flow charts of the packaging method in the embodiment of FIG. 2;

where the metal lead frame body 1

encapsulation layer 10

Redistribution metal layers 111, 112, 113

Metal blocks 121, 122, 123

Metal Block Ⅰ11

Metal Block II 12

Metal block III13

Nickel/gold layers 151, 152

cutting lane 16

LED chip 2

Electrodes 21, 22

Adhesive Ⅰ 31

Adhesive II 32

Fluorescent substance 4

Leads 51, 52

Package 6

Carrier 7

Iron foil 8

Photoresist film Ⅰ 91

Photoresist film I opening pattern 911

Photoresist film Ⅱ 92

Opening pattern 921 of the photoresist film II.

Detailed ways

The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown so that this disclosure will fully convey the scope of the invention to those skilled in the art. However, this invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

Referring to Fig. 1, the technological process of a kind of packaging method of LED of the present invention is as follows:

S101: fixing the iron foil on the carrier plate;

S102: forming a rewiring metal layer on the iron foil;

S103: forming a metal block on the redistribution metal layer;

S104: encapsulating and rewiring the metal layer and the metal block to form a metal lead frame body;

S105: removing the carrier plate and the iron foil;

S106: fixing the LED chip on the surface of the metal lead frame body;

S107: wire bonding;

S108: dot encapsulation, enclosing the LED chip;

S109: cutting into individual packages.

Examples, see Figures 2 and 3

An LED packaging structure, which includes a metal lead frame body 1 and an LED chip 2 , the LED chip 2 is mounted on the metal lead frame body 1 . The metal lead frame body 1 is composed of a metal block I11, a metal block II12, a metal block III13 and an encapsulation layer 10 encapsulating the metal block I11, the metal block II12, and the metal block III13. The metal block III13 is located in the center of the metal lead frame body 1 and occupies the largest area. The metal block I11 is set on the left side of the metal block III13, the metal block II12 is set on the right side of the metal block III13, and the metal block I11 , metal block II12, and metal block III13 are equal in height.

The upper parts of metal block I11, metal block II12, and metal block III13 are rewiring metal layers 111, 112, 113 respectively, and the lower parts are metal blocks 121, 122, 123 respectively, and the metal rewiring layer 111 and the metal The block 121 , the metal redistribution layer 112 and the metal block 122 , the metal redistribution layer 113 and the metal block 123 are fixedly connected up and down respectively. The borders of the redistribution metal layers 111 , 112 , 113 are not smaller than the borders of the corresponding metal blocks 121 , 122 , 123 . Metal block I11, metal block II12, and metal block III13 are usually made of metal copper, with a nickel/gold layer 151 set on the upper end surface and a nickel/gold layer 152 set on the lower end surface to prevent oxidation of the metal copper surface. At the same time, it can also meet the requirements of welding reliability.

The encapsulation layer 10 is formed of an encapsulation resin with good electrical insulation, which connects and fastens the metal block I11, the metal block II12, and the metal block III13; at the same time, the encapsulation layer 10 generally contains oxide Silicon, alumina and other fillers are used to increase the elastic modulus and thermal conductivity of the encapsulation resin and reduce the thermal expansion coefficient, thereby improving the thermal conductivity and reliability of the packaging method.

Adhesive I31 is set on the metal block III13, and the LED chip 2 is fixedly connected to the metal block III13 through the adhesive I31. Heat dissipation. Adhesive I 31 is generally thermally conductive glue or thermally conductive film, mostly silver powder as the main thermally conductive material, and its extension area is preferably slightly larger than the bottom area of the LED chip 2 .

The electrode 21 is electrically connected to the redistribution metal layer 111 of the metal block I11 through the lead 51 , and the electrode 22 is electrically connected to the redistribution metal layer 112 of the metal block II12 through the lead 52 . Therefore, it is better to select the boundary of the re-wiring metal layer to be larger than the boundary of the metal block, which is T-shaped to fix the metal leads 51 and 52 respectively, so that the leads 51 and 52 can be avoided during the SMT (surface mount) process and use. The lead wire 52 is pulled out to improve the mechanical reliability of the product structure. Adhesive II 32 can also be dotted on the top of metal block I11 and metal block II12 to increase the distance between lead wire 51 and the redistribution metal layer 111 of metal block I11, lead wire 52 and the redistribution metal layer 112 of metal block II12. connection strength. Adhesive II 32 is generally thermally conductive adhesive or thermally conductive film, and mostly silver powder is used as the main thermally conductive material.

The upper surface of the metal lead frame body 1 is provided with a package 6 made of silica gel, optical resin, etc., and the package 6 seals the LED chip 2 and the leads 51, 52 in it to protect the LED chip 2 and the leads 51, 52. The outer surface of 6 is convex.

In order to obtain white light, it is necessary to select a chip that emits blue light, and to coat the light-emitting surface of the LED chip 2 with a fluorescent substance 4 of yellow phosphor powder, and to excite the yellow fluorescent substance with blue light to obtain white light, forming a white LED packaging structure.

The technological process of the LED packaging method of the above-mentioned embodiment is as follows:

As shown in FIG. 4 , take a flat carrier 7 and iron foil 8 , fix the iron foil 8 on the carrier 7 , and the iron foil 8 is slightly smaller than the carrier 7 .

As shown in Fig. 5 and Fig. 6, a photoresist film I 91 that can be photoresisted is pasted on the iron foil 8, and the opening pattern 911 of the photoresist film I is formed through successive processes such as pattern setting, exposure, and development.

As shown in FIG. 7, iron foil 8 is used as the conductive layer, and copper is electroplated in the opening pattern 911 of the photoresist film I to form rewiring metal layers 111, 112, 113. The rewiring metal layer 113 is located on the rewiring metal layers 111, 112. between them; electroless nickel/gold plating on the surface of the rewiring metal layers 111, 112, 113, the boundary of the rewiring metal layer 113 is not smaller than the boundary of the LED chip 2; the remaining photoresist film is removed by deglue process.

As shown in Figure 8 and Figure 9, a photoresist film II 92 that can be photoresisted is pasted on the iron foil 8 that has completed the rewiring metal layers 111, 112, 113, and the photoresist film is formed by setting the pattern, exposing, and developing in sequence The II opening pattern 921 exposes part of the rewiring metal layers 111, 112, 113 that have been electroless nickel/gold plated on the surface; the opening size of the photoresist film I opening pattern 911 is not smaller than the opening size of the corresponding photoresist film II opening pattern 921.

As shown in FIG. 10 , metal blocks 121 , 122 , 123 are formed by electroplating in the opening pattern 921 of the photoresist film II with the iron foil 8 as the conductive layer again. The remaining photoresist film is removed through the glue removal process, and then the wiring metal layers 111, 112, 113 are connected one-to-one with the metal blocks 121, 122, 123 to form metal block I11, metal block II12, and metal block III13 respectively. Usually metal block Ⅰ11, metal block Ⅱ12, and metal block Ⅲ13 are all T-shaped, which effectively fixes the metal leads. During the SMT (surface mount) process and use, the metal leads will not be pulled out. The mechanical reliability of the product structure is improved.

As shown in FIG. 11 , the entire iron foil 8 forming the metal block I11 , the metal block II12 , and the metal block III13 is encapsulated to form an encapsulation layer 10 .

As shown in Figure 12, the encapsulation layer 10 on the top of the iron foil 8 is thinned by grinding and polishing, exposing one end surface of the metal block I11, the metal block II12, and the metal block III13, and on the metal block I11, The end faces of the metal block II12 and the metal block III13 are electroless plated to form nickel/gold, forming a nickel/gold layer 151 .

As shown in Figure 13, turn the completed packaging structure up and down 180°, take out the lower plate 7, and corrode the iron foil 8, exposing the other end surfaces of the metal block I11, metal block II12, and metal block III13. The other end surfaces of the metal block I11 , the metal block II12 , and the metal block III13 are electrolessly plated with nickel/gold to form a nickel/gold layer 152 .

As shown in Figure 14, adhesive I31 is placed on the surface of the electroless nickel/gold plated metal block III13, the boundary of adhesive I31 is generally not smaller than the boundary of LED chip 2, and the back of LED chip 2 is passed through Adhesive I31 is attached to the area of metal block III13; wire bonding, the electrode 21 of the LED chip 2 is connected to the redistribution metal layer 111 of the metal block I11 through the lead wire 51, and the electrode 22 is connected to the metal block through the lead wire 52 The redistribution metal layer 112 of II12 is connected.

As shown in Figure 15, on the top of the metal block I11 and the metal block II12, the joints of the lead wires 51, 52 and the metal block I11 and the metal block II12 can also be dotted with adhesive II32 to increase the connection between the lead wires 51 and the metal block II12. The connection strength between the redistribution metal layer 111 of the metal block I11 , the leads 52 and the redistribution metal layer 112 of the metal block II12 .

As shown in FIG. 16 , the fluorescent substance 4 is sprayed on the light-emitting surface of the LED chip 2 , and the LED chip 2 and the lead wires 51 and 52 are wrapped by the dot package 6 . The outer shape of the package 6 usually forms a structure with a light-condensing or light-scattering effect, such as a hemispherical shape, a convex lens shape, etc., to meet the needs of various occasions.

As shown in FIG. 17 , the above packaged LED package structure is cut along the cutting line 16 into individual packages.

An LED packaging method of the present invention is not limited to the above-mentioned preferred embodiment. For example, the number of LED chips 2 can be more than one, and the number can be increased according to product design needs. All chips are arranged above the metal block III13. Block III13 dissipates heat directly, with short heat dissipation channels, small thermal resistance and stable performance.

Any modifications, equivalent changes and modifications made to the above embodiments according to the technical essence of the present invention by any person skilled in the art without departing from the spirit and scope of the present invention all fall within the scope of protection defined by the claims of the present invention.

Claims (10)

1. A method for encapsulating LEDs, the process of which is as follows: Take a carrier plate (7) and iron foil (8), and fix the iron foil (8) on the carrier plate (7); Paste the photoresist film I (91) on the iron foil (8), and form the photoresist film I opening pattern (911) by setting the pattern, exposing and developing in sequence; Electroplate metal in the opening pattern (911) of photoresist film I to form rewiring metal layers (111, 112, 113), and electroless nickel/gold plating on the surface of rewiring metal layers (111, 112, 113), by removing glue process to remove the remaining photoresist film; Paste the photoresist film II (92) on the iron foil (8) that has completed the rewiring metal layers (111, 112, 113), and form the photoresist film II opening pattern (921) by setting the pattern, exposing and developing in sequence , exposing the rewiring metal layer (111, 112, 113); Metal blocks (121, 122, 123) are formed by electroplating in the opening pattern (921) of the photoresist film II, and the remaining photoresist film is removed by deglue process, and then the metal layers (111, 112, 113) and metal blocks (121) are wired , 122, 123) are connected one-to-one to form metal block I (11), metal block II (12), and metal block III (13); encapsulating the top of the iron foil (8) forming metal block I (11), metal block II (12), and metal block III (13), to form an encapsulation layer (10); Thinning the encapsulation layer (10) above the iron foil (8) by grinding and polishing techniques, exposing one end surface of metal block I (11), metal block II (12), and metal block III (13), And the electroless nickel/gold layer (151) is plated on the end faces of metal block I (11), metal block II (12), and metal block III (13); Turn the package structure completed above up and down 180°, remove the download board (7), and corrode off the iron foil (8), exposing metal block I (11), metal block II (12), metal block III (13 ) on the other end face of metal block I (11), metal block II (12), and metal block III (13) by electroless nickel/gold plating (152); Adhesive I (31) is placed on the surface of the metal block III (13) with the nickel/gold layer (152), and the back of the LED chip (2) is attached to the metal via the adhesive I (31). within the area of Block III (13); Wire bonding, connecting the electrodes of the LED chip (2) to the rewiring metal layers of the metal block I (11) and the metal block II (12) respectively through lead wires; Point package (6), the package (6) wraps the LED chip (2) and its leads; The above packaged LED package structure is cut into individual packages. 2. The LED packaging method according to claim 1, characterized in that: the boundary of the rewiring metal layer (113) is not smaller than the boundary of the LED chip (2). 3. The LED packaging method according to claim 1, characterized in that: the opening size of the opening pattern (911) of the photoresist film I is not smaller than the opening size of the corresponding opening pattern (921) of the photoresist film II. 4. The LED packaging method according to claim 1, characterized in that: said metal block I (11), metal block II (12), and metal block III (13) are all T-shaped. 5. The LED packaging method according to claim 4, characterized in that: the heights of the metal block I (11), the metal block II (12), and the metal block III (13) are equal. 6. The LED packaging method according to claim 5, characterized in that: the height of the metal blocks (121, 122, 123) is 100 microns to 200 microns. 7. The LED packaging method according to claim 6, characterized in that: the metal blocks (121, 122, 123) are made of metal copper. 8. The LED packaging method according to claim 1, characterized in that: the material of the rewiring metal layer (111, 112, 113) is metallic copper. 9. The LED packaging method according to any one of claims 1 to 8, characterized in that: after the wire bonding, it also includes the step of: connecting the lead wire with the metal block I (11) and the metal block II (12) Apply Adhesive II (32) to the joint. 10. The LED encapsulation method according to claim 9, characterized in that: before the dot encapsulant (6), a process step is further included: spraying a fluorescent substance (4) on the light-emitting surface of the LED chip 2 .